DS2760 Thermocouple Kit from Parallax in PicBasicPro

[Acetronics2]

Hi,

Why not use the Microchip recommended method ???

use much less than those 400 Words for the table ( What an horror ! ) and make a linear interpolation between two consecutive table values.

As the seebeck coeff is quite constant over wide temp ranges ... it seems obvious !!!

Alain

[mackrackit]

I do not know if this will help, but you are welcome to it.

It uses to tables in code space.

This uses a LM34 for the cold junction and a "K" type thermo-couple.
10 degree F resolution from 510 to 2500. The TC is ran through an op amp.
Even does a little data logging.

'*  Date    : 09/01/2007                                                                                                                                 
'*  Pic   :  18F4320   

   DEFINE OSC 20

DEFINE LCD_DREG     PORTC
define LCD_DBIT     0
DEFINE LCD_RSREG    PORTD
DEFINE LCD_RSBIT    1
DEFINE LCD_EREG     PORTD
DEFINE LCD_EBIT     0
DEFINE LCD_BITS     4
DEFINE LCD_LINES    2
DEFINE LCD_COMMANDUS    2000
DEFINE LCD_DATAUS   50

ADCON1= %00011011  '13 'AN0 and AN1      
CMCON = 7
TRISC = %10111111

temp1        var byte
temp2        var byte
T1			 var byte
T2           var byte

TC	VAR	WORD
TCT	VAR	WORD
TX	VAR WORD
TXI	VAR WORD
TXIU	VAR WORD
TXIU = 500
T_T	 VAR WORD
A_T VAR WORD

DL	VAR	WORD
BCNT	VAR	WORD
CNT	VAR	WORD
BL		VAR	WORD
CNT = 0
BL = 0
D_C		VAR	WORD

INTCON2.7 = 0
T0CON = %11010111
INTCON = %10100000 'Enable INTE interrupt
On interrupt goto myint 

START:
    pause 1000
    LCDOUT $FE,1,"MACKRACKIT CONTROLS" 
    lcdout $FE,$C0,"PYROMETER V2"
     pause 5000

INTCON.2=0

RUN:
gosub getT1
GOSUB getT2

T1 = temp1 
A_T = T1 - 30
T_T = A_T + TXIU
LCDOUT $FE,1,"LM34 ",#T1," A_T ",#A_T

lcdout $FE,$C0,"TC ",#TXIU," T_T ",#T_T
GOSUB D_INDEX
IF TXIU < 1760 THEN M_H
IF PORTD.3 =1 THEN E_D
	GOTO RUN

M_H:
LCDOUT $FE,1,"MORE HEAT "
PAUSE 50
GOTO RUN

getT1:
	ADCON0= %00000001  '$1  '%00000001 AN0
ADCON2.7 = 0
	gosub getAD
	temp1 = ADRESH
	return
	
getT2:
	ADCON0= %00000101   '$5  '%00000101 AN1
ADCON2.7 = 1
	gosub getAD
	TC.highbyte = ADRESH
	TC.lowbyte = ADRESL
	return

getAD:
	pause 50
	ADCON0.1 = 1
	pause 50
	return

	END


D_INDEX:
TX = TC 
'THERMO STEPS
LOOKDOWN2 TX,>[898,895,892,889,886,883,879,876,873,870,867,863,860,857,854,850,_
847,844,841,838,835,832,828,825,822,819,815,812,809,805,802,799,795,792,788,785,_
782,778,775,772,769,765,762,758,755,751,748,744,741,737,734,731,727,724,721,717,_
713,710,706,703,699,696,692,689,685,682,678,675,671,667,664,660,656,653,650,646,_
643,639,635,632,628,624,620,617,614,610,606,603,599,595,592,588,584,580,577,573,_
570,566,562,558,555,551,547,544,540,536,532,529,525,521,517,513,509,506,502,498,_
495,491,487,483,479,475,471,468,464,460,456,453,449,445,441,437,433,429,426,422,_
418,414,410,406,402,398,395,391,387,383,379,375,371,367,363,360,356,352,348,344,_
340,336,332,328,324,321,317,313,309,305,301,297,293,290,286,282,278,274,270,267,_
263,259,255,252,248,244,240,236,232,229,224,221,217,213,209,206,202,198,194,190,_
187,183,180,176,173],TXI



'THERMO TEMPERATURES
LOOKUP2 TXI,[2500,2490,2480,2470,2460,2450,2440,2430,2420,2410,2400,2390,2380,2370,_
2360,2350,2340,2330,2320,2310,2300,2290,2280,2270,2260,2250,2240,2230,2220,2210,2200,_
2190,2180,2170,2160,2150,2140,2130,2120,2110,2100,2090,2080,2070,2060,2050,2040,2030,_
2020,2010,2000,1990,1980,1970,1960,1950,1940,1930,1920,1910,1900,1890,1880,1870,1860,_
1850,1840,1830,1820,1810,1800,1790,1780,1770,1760,1750,1740,1730,1720,1710,1700,1690,_
1680,1670,1660,1650,1640,1630,1620,1610,1600,1590,1580,1570,1560,1550,1540,1530,1520,_
1510,1500,1490,1480,1470,1460,1450,1440,1430,1420,1410,1400,1390,1380,1370,1360,1350,_
1340,1330,1320,1310,1300,1290,1280,1270,1260,1250,1240,1230,1220,1210,1200,1190,1180,_
1170,1160,1150,1140,1130,1120,1110,1100,1090,1080,1070,1060,1050,1040,1030,1020,1010,_
1000,990,980,970,960,950,940,930,920,910,900,890,880,870,860,850,840,830,820,810,800,_
790,780,770,760,750,740,730,720,710,700,690,680,670,660,650,640,630,620,610,600,590,_
580,570,560,550,540,530,520,510,_
500],TXIU

RETURN

'*****Interrupt Handler *****
Disable 'No interrupts pass this point
myint:
	CNT = CNT + 1
SEROUT2 PORTE.2,16468,[DEC CNT,13,10]
	IF CNT => 1045 THEN   '1830 = 1m 45 s - 10457 = 10 m- 1045 = 1 m
	HIGH PORTD.2
	PAUSE 100
	LOW PORTD.2
	PAUSE 100
	CNT = 0
SEROUT2 PORTE.2,16468,[DEC 11,13,10]
GOSUB	W_D
		ENDIF

'PIR1.0=0
INTCON.2 = 0 'clear interrupt flag
resume 'return to main program

enable


W_D:
INTCON = %10000000 'DIS-Enable INTE interrupt
FOR BCNT = 1 TO 10
	HIGH PORTD.2
	PAUSE 100
	LOW PORTD.2
	PAUSE 100
NEXT
BCNT = 0
READ 200, DL.BYTE0
READ 201, DL.BYTE1
'DL = DL + 2
WRITE 200, DL.BYTE0
WRITE 201, DL.BYTE1
WRITE DL, TXIU.BYTE0
WRITE DL+1, TXIU.BYTE1
INTCON = %10100000 'Enable INTE interrupt
RETURN


E_D:
INTCON = %10000000 'DIS-Enable INTE interrupt
	FOR BL = 1 TO 100
READ 0, D_C.BYTE0
READ 1, D_C.BYTE1
	HIGH PORTD.2
	PAUSE 100
	LOW PORTD.2
	PAUSE 100

LCDOUT $FE,1,"TXIU  ",#D_C

SEROUT2 PORTE.2,16468,["MACKRACKIT ",DEC D_C,"  ",DEC DL,13,10]
NEXT
INTCON = %10100000 'Enable INTE interrupt
GOTO RUN

[seanharmon]

Im an idiot. I overlooked the Microchip application note that Alain mentioned.

I found a larger table for thermocouple type K.(I originally used the type T table because it was smaller) http://srdata.nist.gov/its90/download/type_k.tab
A large portion of the table can be removed because eventually I plan to measure temps in the range of 30Fto700F. With the decimal place shifted it should work in PBP?

Its been years since Ive taken calculus, and was wondering what would be the easiest route to take in making the table smaller and then using linear approximation to figure the in between values. I understand that it uses floating point math which PBP doesnt do normally.

Any help would be greatly appreciated.

Once again thanks Alain and Dave. (im getting there...slowly)